1. Field of the Invention
The present invention relates to a frame for a cathode ray tube, and, more particularly, to a frame for a cathode ray tube in which the shape of beads formed on the frame or the number of the beads is improved to increase the rigidity of longer sides of the frame.
2. Description of the Related Art
A conventional cathode ray tube will be described hereinafter with reference to FIG. 1.
FIG. 1 is a sectional view illustrating a structure of a conventional cathode ray tube. As shown in FIG. 1, the conventional cathode ray tube includes a panel 1, a funnel 2, a shadow mask 3, an electron gun 4, a deflection yoke 5, a frame 6, a spring 7, and an inner shield 8.
Operation of the cathode ray tube having the above-mentioned configuration will be described. An electron beam, which is emitted from the electron gun 4 travels toward the panel 1, and is then vertically and horizontally deflected by the deflection yoke 5, which is arranged at a neck of the funnel 2.
The deflected electron beam passes through slots formed through the shadow mask 3, and reaches a screen coated on an inner surface of the panel 1. The screen emits light, using the energy of the electron beam, so that an image is reproduced.
The frame 6, which is also included in the cathode ray tube, supports the shadow mask 3. The spring 7 is arranged to tightly fit the frame 6 with an inner surface of the panel 1.
If the electron beam is influenced by an external geomagnetic field, the travel path of the electron beam is deflected, so that the color purity of the reproduced image is degraded. The inner shield 8, which is included in the cathode ray tube, is adapted to reduce the influence of the geomagnetic field.
Meanwhile, the frame 6 must be subjected to treating processes such as a high-temperature heating process and a welding process so that the frame 6 can be used for cathode ray tubes. During the treating processes, however, a vertical load is applied to the frame 6 at one side of the frame 6, so that the frame 6 may be twisted.
Also, the cathode ray tube is subjected to a drop impact test after the manufacture thereof. However, the frame 6 may be deformed during the drop impact test where the frame 6 has a low rigidity. Where the frame 6 is deformed, the position of the shadow mask 3 varies due to the deformation of the frame 6. In this case, the electron beams cannot strike target portions of a phosphor surface, so that a degradation in the color purity of the reproduced image occurs.
Meanwhile, it is possible to reduce the weight and manufacturing costs of the cathode ray tube by reducing the thicknesses of the materials used to manufacture the cathode ray tube. However, the reduction of the thickness of the frame 6 may cause a serious problem associated with the rigidity of the frame 6.
In order to solve this problem, it is necessary to increase the rigidity of the frame 6. However, where the rigidity increase is achieved by increasing the thickness of the frame 6, there is a problem in that the weight and manufacturing cost of the cathode ray tube increase. In order to eliminate such a problem, beads may be formed on the frame 6. This method will be described in detail with reference to FIG. 2.
FIG. 2 is a perspective view illustrating a conventional frame, on which beads are formed. As shown in FIG. 2, the conventional frame, which is designated by reference numeral 6, has a substantially rectangular structure having longer sides extending along a longer axis x and shorter sides extending along a shorter axis y. The frame 6 also has a side wall 6a welded to a shadow mask, and a bottom wall 6b bent from a lower end of the side wall 6a substantially in perpendicular to the side wall 6a. 
Beads 6c are formed on the frame 6. The beads 6c may have various shapes. For example, the beads 6c may have a substantially rectangular shape, as shown in FIG. 2.
Although the beads 6c may be designed to have various arrangements and shapes on the frame 6, the numbers of the beads 6c at the longer and shorter sides of the frame 6 are equal in general cases. Also, the shapes of the beads 6c at the longer and shorter sides of the frame 6 are identical or similar.
In such a case, however, there is a problem in that, when the same load is applied to both the longer and shorter sides of the frame 6, stress is concentrated on the longer sides of the frame 6 because the longer frame sides have a length relatively larger than that of the shorter frame sides. For this reason, the longer sides of the frame 6 have a structure relatively weak against temperature variation and torsion caused by a load applied to the frame 6 at one side of the frame 6. In other words, the rigidity difference between the longer and shorter sides of the frame 6 increases, so that the rigidity of the frame 6 is generally reduced.